Fading and drifting
FM range is limited to about 25 miles (40 km), except for some high power stations.
If a vehicle is moving away from the desired station's transmitter, the signal will tend to fade and/ or drift. This condition is more prevalent with FM than AM, and is often accompanied by distortion.
Fading and drifting can be minimized to a certain degree by careful attention to fine tuning or selection of a stronger signal.
Static and fluttering
When the line-of-sight link between a transmitter and vehicle is blocked by large buildings or mountains, the radio sound may be accompanied with static or fluttering because of the characteristic of FM.
In a similar effect, a fluttering noise is sometimes heard when driving along a tree-lined road.
This static and fluttering can be reduced by adjusting the tone control for greater bass response until the disturbance has passed.
Because of the reflecting characteristics of FM, direct and reflected signals may reach the antenna at the same time (multipath) and cancel each other out.
As a vehicle moves through these electronic dead spots, the listener may hear a momentary flutter or loss of reception.
When two FM stations are close to each other, and an electronic dead spot, such as static or multipath area, interrupts the original signal, sometimes the stronger second signal will be selected automatically until the original one returns.
This swapping can also occur as you drive away from the selected station and approach another station of a stronger signal.
Compact disk player
To avoid damage to compact disc player and discs.